Iterative cardiac output measurement for optimizing cardiac resynchronization therapy: a randomized, blinded, crossover study.

Background: Many invasive and noninvasive methods have been proposed for guiding optimal programming of cardiac resynchronization therapy (CRT) devices. However, results are not satisfying. Preliminary results suggest that cardiac output (CO) measurements using inert gas rebreathing (IGR) might be an eligible method to tailor atrioventricular (AV) and ventriculo-ventricular (VV) programming.